1. Field of the Invention
The present general inventive concept relates to a capsulated colorant, a method of preparing the same, and an ink composition including the capsulated colorant, and more particularly, to a capsulated colorant in which a polymer resin with a cross-linked structure is coated on a surface of a colorant and an ink composition which can be used to simultaneously realize characteristics of excellent waterfastness, lighffastness, rubfastness, and optical density and realize images having excellent durability and printed gloss by containing the capsulated colorant having an extent of cross-linking which is varied.
2. Description of the Related Art
In inkjet printers, a coloring agent is generally defined as a material that exhibits a unique color by selectively absorbing or reflecting visible light. Coloring agents can be divided into dyes and pigments.
A dye is a coloring agent that is printed on and absorbed into a material, such as fiber, leather, fur, paper, or the like, so that the printed material has excellent color fastness with respect to solar cleaning, rubbing, and the like. A pigment is a micro particle having a coloring agent, and is not directly absorbed into but is instead adhered to the surface of a material using a physical method, such as adhesion or the like, so that the printed material has a unique color.
Dyes are mixed and dissolved in solvents, such as water, or the like, but pigments are generally not dissolved in the solvents. Therefore, a crucial aspect for forming pigments is to uniformly disperse pigment particulates in solvents and thereby, allow the formed dispersed state to remain stable permanently without re-aggregation.
Water-soluble dye-type ink is highly superior in terms of long-term storage stability, it keeps its uniformity and has clear color and brightness, however this ink is poor in waterfastness, lighffastness, etc.
Pigment type ink has high optical density (OD), good waterfastness and lighffastness and little bleeding among colors, however this ink is poorer in clarity of color tones and has weaker stability of long-term storage than the dye-type ink. In addition, images which are printed using the pigment type ink have poor dryfastness and wetfastness, that is, rubfastness.
Also, when printing in colors (multicolor printing) with dyes or pigments, bleeding occurs at interfaces of the colors, thereby reducing clearness of printed images.
Therefore, there is still a need for an ink composition which has excellent storage stability like water-soluble dye-type ink, has excellent waterfastness like pigment type ink, and also has improved printed gloss and rubfastness.
To enhance the rubfastness of ink, a method of adding a resin to an ink composition has been proposed. However, there is still an unsolved problem in that the viscosity of ink is increased due to the addition of the resin. In addition, to prevent the increase in the viscosity of ink, a method of adding resin particles to ink has been proposed. However, since the resin particles and pigments are separately dispersed in the ink which has resin particles added thereto, improvement in rubfastness of ink is not sufficient.
Therefore, addressing the above problems by adding new additives to an ink composition is limited. Accordingly, there is a need to improve properties of an ink composition by modifying a colorant used therein.